Telescope of unvariable length and progressively-variable magnification.



H. JACOB. 4 TELESCOPE OF UNVARIABLE LENGTH AND PROGEESSIVBLY VARIABLE MAGNIFIGATION.

APPLICATION FILED APR. 1, 1913.

Patented Nov. 3, 1914.

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Fig.1.

Fig.2.

f if HEm'R-ICH JACOB, 0F STEGLITZ, BERLIN, GERMAN 1, A$SIGNOR T4] E OPTISCHE ANSTALT C. P. GOIERZ AKTIENGESELLSCHAFT. OF FRIEDEi BERLIN, GERMANY.

TELESCOPE D1 UNYARIAELE LENG'E'H AND PROGRESSIVELY-VARIABLE CATION.

Specification of Letters Patent Patented h v. 3.

To all whom it may concern Be it known that I, Hemmer; discos, citizen of the German Empire, and resident of Steglitz, near Berlin. Germany. have invented certain new and useful improve- .ments in Telescopes of llnvariable Length and Progressively'Variable hlagnification. of which the following is a specification The invention relates to improvements in telescopes of unvariable length and progressively variable magnification and its main object is to obtain the progressive change of the magnification with a very short instrument and with the use of very simple means. To thisend a lens system and a multiple system 6f reversing prisms is inserted between the objective of the instrument and its image plane, which systems are movably arranged and connected with each other in such a way that the elements of the system of prisms eliminate by the change of the length of the light path effected by them at their adjustment the displacement of the image plane of the objective efiected by the displacement of the lens system. a

The invention is illustrated in the draw-, ing. in which- Figure 1 shows the optical elements of a telescope, in the objective focus of which a convex lens for varying the focal distance oi the objective is movably arranged; Fig. 2 represents the same optical elements illustrated in Fig. 1 in which, however, the lens for changing the magnificatiou assumes another position with relation to the objective whereby the instrumentis shortened; Fig. 3 illustrates the simultaneous insertion .of a convex lens for changing the image magnification and of a system of reversing prisms for eliminating the change of the length of the instrument, the coupling between the lens and the reversing system being omitted, and the convex lens and the one prism of the reversing system being shown in two different positions; Fig. i is a perspective view of the optical instruments shown in Fig. 3. Fig. 5 is a longitudinal section of a telescope having an optical systern, such as shown in Figs. 3 and i.

The objective is designated by the refer-' ence numeral 1 throughout the drawing.

2 is the ocula, 3 designates the exit pupil, 4 designatesan axially movable convex lens magnification is reduced.

for changing'the objective ll); and 6 designate the two recta prisms of a Porro reversing s 7 are the outlines of a "flflgfid in the image plane.

In the embodiment shown in convex lens a. is located in the focus ofthe objective 1. in this position the lens s has only the effect that it causes the rays passing through the instrument to converge somewhat toward the ocular If the lens 4 is moved toward the objective it effects. as Fig. 52 clearly shows. that the image piane is approached to the objective and that the in the arrangement shown in Fig. I) the Porro reversing system of ins .1, 6 is still inserted between the objective and the image plane into the path of the rays,

l which system permits by the relative displacement of its prisms that thechange of the length of the path Which'is due to the displacement of the lens 4 compensated so that the length of the instrument does not need to be changed. The orism 6 is supposed to be movable. The drawing; shows the position oi the parts for two 'difierent magnifications, the one position of the movable parts being slu'nvn in full lines and the other position thereof being shown in dotted lines.

In the instrument shown in Fig. 5 the 8 optical elements are designated with the same numerals as the corresponding parts in Figs. 3 and i. is the casing of the lnSllll'x ment, having a sc ew threaded shaft 9 mounted therein, with an actuating knob 10. The shaft 9 has two separate screw threads 11 and 12, which are of (lifter-cut pitches. The screw thread 11. is engaged with a non rotatable nut 13 having the prism 5 fixed to it; the screw thread 12 carries a nut 14 vforming a non-rotatable mounting for the lens a. On rotation of the knob 10 the nuts 13 and 1% are s ifted lengthwise on-the shaft 9, and carrying with them the prisms G and lens 4 respectively, the pitches of the-screw threads-ll and 12 being so proportioned that the image plane of the instrument remains unchanged.

What I claim is: 1 I

1. In a telescope in combination with an objective and an ocular arranged at a subsyslonn 5 the oheingo of "b': length of tho light path (-ll'uvlod by iheii' dis pliiconicntf compenszm? the (usplnwinont of tho nymgl o plano cfi'ol'l'm'l by tho ndjnstnnml oi the lens .Uni.

i. In a tolosco 'w in (-ombinnlion will: an objective and an ()(Hlil arranged at a sail, slantiolly um'iii'inble distzancv from L'JQll other. an axiii l adjustable lens system positioned within ll path of rays between said objective and said ocular :nhipiod to coop :1 ate with said objective so as to form with i compound system liming an image plane positioned dependence from the position oi the objective Wllll relation to that of the adjustable lens wsiein and a Poi-roprism systm-n in between snio objeci'iwand adjustable lens system, the clistiinve of its elements adapted to be adjusted. so as lo compensaicthe displacement of the image plane of the led within the path of objccl'ive on displacement of the adjustable lons system.

fl. ln 2: lolcsoope in combination with an l of the objevtivo with relation to that of the jzidjllslzible lens system and a Porto-prism s 'sloin inserted within the path of rays b'c- {ween said objective and adjustable lens systenn one of its, elements being fixed and the other nmvnble in axial direction so as "[0 vonipensale the displacement of the ima o plane of the objective on displacement of t 1e adjustable lens system. y

In testimony whereof I have signed this specification in the presence of two subscribing witnesses.

HEINRICH JACOB. li messes:

HENRY HASPER. l l owmmn HAUPT. 

